Tractor fuel and process of making same



Patented Mar. 5, 1946 7M. SlEhnull TRACTOR FUEL AND PROCESS OF MAKINGSAME Rodney V. Shankland. Chicago. 111.. assignor to Standard OilCompany, Chicago, Ill., a corporation of Indiana No Drawing. ApplicationJune 20, 1941,

Serial No. 398,947

4 Claims.

This invention relates to an improvement in tractor fuels and moreparticularly to a method of making tractor fuels by catalytic processesin which light hydrocarbons are converted at high temperatures withsolid catalysts and the products are fractionated to the desired boilingrange. One object of th invention is to produce a synthesized, heavy,volatile hydrocarbon fuel for use in internal combustion engines of thetype employed on tractors, which fuel has less tendency to causedetonation and provides smoother operation of the tractor than do fuelsordinarily available. Another object of the invention is to convert lowboiling hydrocarbon distillates into a valuable liquid tractor enginefuel having superior properties, either when used alone or when blendedwith other tractor fuels having an undesirable tendency towarddetonation.

Tractor fuels commonly employed heretofore have been made by thedistillation of crude petroleum oil or thermal cracking still products.They have had a distillation range generally overlapping the upper endof the gasoline boiling range and the lower end of the kerosene boilingrange, even extending through the kerosene boillng range. Enginesemploying these fuels ordinarily operate at a higher temperature thangasoline engines and at a lower compression ratio, e. g., 4:1, althoughthe compression ratio may be as high as 5:1 or 5%:1. Unlike solidinjection engines, these tractor engines vaporize the fuel beforeignition. For this reason the distillation characteristics of the fuelare quite important.

Tractor engines using this fuel operate with a high intake manifoldtemperature as a result of which they are not adapted to burninggasoline because of excessive thermal expansion which has the effect ofthrottling the engine. Thus, the intake manifold temperature of thetractor engine under avera e load conditions is typically in the rangeof 250 F. to 300 F. whereas a gasoline engine operating under the sameload conditions will have an intake manifold temperature of only about180 F. The manifold temperature of the tractor engine is consistentlyabout 50 to 100 F. higher than that of the gasoline engine.

Recently, there has been developed for tractor engines a special fuel,herein called light tractor fuel. which is characterized by a relativelylow initial boiling point and low distillation point but having aboutthe same maximum boiling point as tractor fuels heretofore used.Following are typical A. S. T. M. distillation ranges for heavy and"light tractor fuels of the types heretofore used:

Heavy Light fuel fuel specification F. Initial boiling point 215 67 F-(minimum). 10% off 372 210 F. (maximum).

419 284 F. (minimum).

472 460 F. (maximum). End point 506 510 F. (maximum).

In one example such a heavy" fuel had an A. P. I. gravity of 42.6, anopen cup flash point of 93 F. and sulfur content of about 032% to .05%.The knock rating of this fuel by the regular A. S. T. M. motor methodwas about 37.1 octane number. The specification for the light fuel justdescribed also includes an octane number of at least 40 A. S. T. M. andan octane number of 50 to is frequently desired for more recent designsof engines running at higher speeds, for example. 1500 R. P. M. insteadof 800 R. P. M. previously.

I have now discovered that I can prepare, by catalytic conversionmethods applied to petroleum distillates, a superior tractor fuel havinga much higher octane number and also a higher boiling range and lower A.P. I. gravity than tractor fuels heretofore employed. In making thisfuel I prefer to convert the heavy naptha fraction of crude petroleum.The crude petroleum fraction or virgin naptha employed may have adistillation range of about 250 F. to 450 F. Considerable variation inthe boiling range is permissible, however, and I may employ napthastocks having an end point within the gasoline boiling range, forexample, about 400 F., or I may employ somewhat higher boiling napthas,boiling up to about 500 F. Another naptha suitable for this purpose mayhave a boiling range of 300 F. to 425 F. In general, fractions boilingat least largely within the range from 250 F. to 450 F. are mostsuitable.

The catalytic operation is generally carried out by first vaporizing thenaptha and conducting the vapors at conversion temperatures of the orderof 850 F. to 1050 F. in contact with a catalyst, usually of thedehydrogenation type. For this purpose I may use a catalyst composedessentially of an oxide of a metal of the left column of the VIth groupof the periodic system. preferably in combination with active alumina,although the oxide of vanadium and oxides of other metals of the leftcolumns of the IVth and Vth grou s may also be u ed alone or incombination with each other. Molybdenum oxide and chro ium oxide areverv effective and their effectiveness is enhanced by alumina used as asu port. The With group metal oxide is preferably present in a minorproportion in the mixture. for exam le. 2 to 25%. The catal st may bemade by impregnating activated bauxite or active alumina or ma nesiawith ammonium chromate. ammonium molybdate. chromium nitrate or othersuitable. salt and subseouently heating the catalyst mixture. Thecatalyst may be employed in the form of a powder or in ranular form.either suspended or maintained in a porous fixed bed through which thenaptha. vapors are passed.

In processing na'p a I prefer to maintain a hydrogen pressure with n thecatalyst zone and this may be. accom lished .bv l' ixin hydro en withthe na'otha va ors entering the reaction chambe or by adding super ea edr en directly to the react on chamber. H dro en for th s ur ose. may beobtained lar el f om the hydro enmws ases produced in the proc ss and ifdesired t se bvdro einnus ga es conta ni g about 40 to 80% of hydro enby vo ume may be dire tl recvoled fr the as Senar tm' o t e reac i n camber, The pressure emnloved in the reac on chamber will preferab y beof the order of 50 o 450 p unds per souar inch and the amount Of hy roen is meierahlv about 1 t 3 mole per mol of naphtha h drocar on treated.

The hydrogen pressure is insufilcient to effect hydro enation of thehvdrocarbon products and the react on occurrin a pears to he one ofdehydro enat on accompanied by olyme zation and con e sa ion of t e ntrmedi te roducts to hi her boilin hydrocarbons suitable f r tractor fues. The. rate of contact ng the na tha vapors with the catalyst ispreferably about 0-2 to volumes of l ould naotha per hour p r apparentvolume of catalyst (0.2 to 10 V. H. V).

As a specific exam le of catal tic nantha conversion. an East Texasstrai ht run heavy naot a was subjected to the action of a catalystcontaining about 10% of active molvbdena on active alumina. The na'othafeed has approximately the following characteristics:

The temperature in the reactor was 930 F. to 990 F.. vary ng somewhatwith the age of the catalyst. About 2% of tractor fuel was obtained inthis operation having the following characteristics:

Gravity-A. S. T. M 12 Initial boiling point F.. 430 10% .F' 461 90% F566 After the reaction has proceeded for a period of time. generallyfrom 1 to 20 hours. the catalyst activity is diminished by thedeposition of carbonaceous matter thereon. It is accordingly desirableto divert the hydrocarbon vapors to another catalyst chamber andregenerate the spent catalyst by blowing with air or oxygen-containinggases to remove carbon by combustion. The temperature of regeneration ispreferably kept below 1200 F. and generally in the range of 1000 F. to1100 F. After regeneration the catalyst is ready for reuse and thisregeneration may be repeated almost indefinitely.

The products from the catalytic operation are separated by fractionationinto gas, gasoline and higher boiling synthetic fuel fractions. Theheavier fractions boiling above the gasoline boiling range constituteabout 2 to 10% of the naptha charged to the process. This material mayhave a boiling range of about 400 F. to 600 F. but the boiling range maybe narrowed by redistillation to about 425 F. to 550 F. This fractionmay be used directly as a tractor fuel but it is preferred to blend itwith other stocks especially stocks boiling in a lower distillationrange, the amount of such other stock being about 25 to of the blend.Stocks suitable for this purpose may be virgin or cracked kerosene orvirgin heavy naptha. One of the characteristics of the polymer fractionis its very low A. P. I. gravity or high density which may equal or evenexceed the density of water. A. P. I. gravities of 9.5 to 12 are readilyobtainable, and the gravity is generally in the range of about 10 to 20A. P. I. The high density of this fuel corresponds to a higher weightper gallon which is especially desirable for tractor operators whopurchase the fuel on a volume basis. Accordingly, this fuel provides thetractor operator with a larger actual amount of fuel or power per gallonsimultaneously with increased knock resistance which increases thesmoothness of tractor operation.

Following are typical distillation inspections for my synthesizedtractor fuel:

The refractive index of the above unblended fuel was 1.583 and the A. P.I. gravity 12.2.

One of the characteristics of my synthetic tractor fuel is its highblending value which means that when blended with ordinary tractorfuels, it improves the knock rating of that fuel to a higher degree thanwould be expected from the amount employed on a straight proportionalbasis. The following table shows the results obtained:

Octane numberA. S. T. M. ordinary tractor fuel 37.1

' 90% ordinary tractor fuel plus 10% syn- 100% synthetic tractor fuel 90The knock rating of my synthetic fuel is above 80 and generally between80 and A. S. T. M.

ing my relatively heavy synthetic tractor fuel with lower boilingfractions of the ordinary tractor fuel heretofore employed. Thus, alight fraction was made by distilling oil. 60% from ordinary tractorfuel. When this was blended in the ratio of 90 parts to parts ofsynthetic tractor fuel, the knock rating A. S. T. M. was increased from41.9 to 48. When blended in the ratio of 80 to 20, the knock rating, theA. S. T. M., of this same light tractor fuel was increased to 54. Inanother example, blending 20 parts of the synthetic fuel with 80 partsof a Mid-Continent virgin heavy naptha increased the knock rating, A. S.T. M., from 25.5 to 43.2. All ratios given here for blending are inparts by volume.

The blended fuel obtained in this way has a wide boiling range whichincludes those light constituents of the virgin fuel having the bestknock rating and the heavy high knock rating constituents of thesynthetic fuel. As a result, I obtain more uniform performance with thisfuel under engine operating conditions where segregation of the fueloccurs due to partial vaporizaproximately that of heavy naptha andabout;

10 to per cent of a synthetic hydrocarbon polymer fraction having ahigher boiling range than the boiling range of said naptha prepared bycontacting a petroleum naptha at conversion temperature in the presenceof added hydrogen; with a dehydrogenation catalyst and recovering fromthe product a polymer fraction boiling in the range of about 400 to 600F. with an A. P. I.

gravity of about 10 to 20, and a knock rating above about A. S. T. M.

2. A light tractor fuel as described in claim 1 further characterized inthat the finished tractor fuel has an initial boiling point of about 356F. and a maximum boiling point of about 520 F.

3. The method of preparing a tractor fuel of high knock rating whichcomprises blending with a low knock rating heavy petroleum napthaboiling substantially within the gasoline boiling range about 10 to 40per cent of a synthetic polymer fraction boiling in the range of about400 to 600 F. with a gravity of about 10 to 20 A. P. 1.. derived fromthe conversion of a heavy petroleum naptha by contact with adehydrogenating catalyst at conversion temperature and in the presenceof added hydrogen.

4. The process of claim 3 wherein said heavy petroleum naptha ischaracterized by. a knock rating of about 25.5 to 42 A. S. T. M.

RODNEY V. SHANKLAND.

:1 F a 4 u .r 130. ULS) l \\U\J 2,895,976 3 Certain advantages are alsoobtainable by blenda petroleum distillate having a boiling range ap K

